78 



NORMAL AND EXPERIMENTAL POLLINATION. 



but flew away immediately. Between such visits they stopped at normal 

 flowers and sipped nectar. Halictus pulzenus behaved in a similar manner. 

 Flowers sprinkled with talcum one day lost their odor during the night and 

 the following day were visited normally by both Bombus juxtas and Halictus 

 pulzenus for nectar. 



Cotton-wads sprinkled with peppermint or almond essence were 

 placed below the calyxes of 28 mature flowers, and 28 noimal ones were 

 left for comparison, with the results shown in table 54. 



Table 54. — Visitors to normal and scented flowers. 



Species. 



Normal 

 flowers. 



lint 



Peppermint Almond 



scented. scented. 



Bombus juxtus 



bifarius 



proximus. . . . 



Prosopis basalis 



Andrena madronitens 

 Osmia bruneri 



Total 



8:38 



6:27 



0:0 



3:4 



1:1 



1:1 



5:5 

 0:0 

 1:1 

 0:0 

 0:0 

 0:0 



19:71 



0:0 

 0:0 

 0:0 

 0:0 

 0:0 

 0:0 



SUMMARY. 



Practically all visitors solved successfully the problems involved in 

 changes of position, inverted flowers being visited as much as normal ones 

 at least. On the other hand, a light plug of cotton rendered all visits 

 unsuccessful. When the styles, stamens, and staminode were removed 

 in Pentstemon glaber, most of the visitors left without securing nectar, while 

 in the case of P. glaucus with the staminode excised, Bombus juxtus entered, 

 backed out, and then went in again to the nectar. When the lips were 

 separated in P. glaber, about half the visitors flew away as if disturbed. 

 With the lobes split to the base, landing was modified to a marked degree, 

 but it became impossible only in the case of one or two species. The 

 removal of the upper lip produced no effect, but with the lower lip shortened 

 or removed, the larger bees, such as Bombus and Apis, were unable to land 

 on the small flowers of P. gracilis, while Osmia was obliged to make use of 

 the staminode for landing. Splitting the upper lobes to the base in P. 

 gracilis caused Bombus to inspect merely or to fly away without securing 

 nectar, while splitting the lower ones in P. glaber caused difficulty in alighting 

 even to smaller bees such as Osmia. When the interior of the flower was 

 disarranged by slipping a corolla over the staminode, Osmia failed to find 

 an entrance. 



Artificial flowers of P. glaber secured no visitors whatever, but natural 

 flowers painted with water-colors were well visited. The addition of honey 

 had practically no effect, while essences greatly reduced the visits to P. 

 secundifiorus. Flowers scented with peppermint received one-third as 

 many visitors and one-twelfth as many visits as the normal ones. Those 

 scented with almond were completely shunned, in marked contrast with the 

 behavior in Chamaenerium. 



